Safeguarding Harvests: The Seed’s Role in Plant Protection

You might not be familiar with the fungus Aspergillus, but farmers who produce our food certainly know about it. Aflatoxin is a harmful, cancer-causing compound produced by certain species of Aspergillus. This toxin is found in various agricultural commodities, such as corn, cotton seeds, and nuts. It also lurks in soil, decaying vegetation, hay, and stored grains, especially during warm and moist conditions.

Aflatoxin poses a serious threat to our food supply as it can contaminate crops, significantly reducing food production in regions like the southern United States. Here, the hot, dry climate creates ideal conditions for fungal growth and aflatoxin production.

“Aflatoxin is a major problem,” explains Dr. Hamed Abbas, a plant pathologist at the Agricultural Research Service’s Biological Control of Pests Research Unit in Stoneville, Mississippi. “In 1999 and 2000, many farmers experienced complete crop loss due to an aflatoxin epidemic. Historically, the South faces an aflatoxin outbreak roughly every decade.”

High levels of this toxin can jeopardize the health of humans, pets, fish, livestock, and even wild animals such as migrating birds. Aflatoxin is known to cause acute and chronic liver injury and liver cancer. Agricultural Research Service (ARS) scientists and their collaborators have dedicated years to developing fungal strains to protect soil and plants. They use a “good” strain of Aspergillus flavus, which competes with harmful fungi to prevent crop contamination.

A newer method for delivering this protective fungus involves coating crop seeds with a natural mixture, including the beneficial Aspergillus flavus strain, using corn-starch-based bioplastic and biochar.

“The seed is underground, so you need to protect it from bad fungi by adding the good fungi,” says Abbas. “The idea is competition—whichever fungi arrive first can control the plant. By treating the seed with good fungi, you prevent the bad fungi from taking over.”

Biocontrol methods utilizing beneficial fungi have become a crucial strategy for combating aflatoxin contamination in essential crops across the southern U.S. and other parts of the world. While Aspergillus strains have shown efficacy, current delivery methods can be wasteful, and the fungus must be applied before growers know if aflatoxin will be an issue for the season.

Abbas and his team have converted their fungal Aspergillus bioplastic, used for years to fight aflatoxins on crops, into a slurry. This slurry is a coating made from corn starch and other biodegradable materials, allowing the fungus to adhere to seeds. The team used this slurry to coat seeds of crops like corn, peanuts, and others vulnerable to aflatoxins before planting. The coating serves as a physical barrier, preventing harmful fungi from infiltrating the plant.

“The coating enables the bioplastic particles to dry into a hard, durable layer on seeds, incorporating agrochemicals and biocontrol microorganisms in a form that resists dust-off of the incorporated agents,” Abbas explains. “It’s completely biodegradable and environmentally friendly.”

Having seen success with corn, Abbas is now testing this technology on other crops, such as soybeans and peanuts. They are also adding biochar, a soil-enriching ingredient, to the seed coating.

“Biochar can enhance plant health and help it cope with stresses like drought,” Abbas says. “A healthy seed leads to a healthier yield, benefiting both farmers and consumers.”

Biochar is already widely used to improve soil quality. Abbas’s team is adding biochar from plant waste, such as peach pits and grape stems, as well as hardwood or coconut shells, to their bioplastic seed coatings. They are also investigating whether coating seeds with biochar will provide nutrient benefits to crops in subsequent years.

“When you add biochar to the soil, it takes time to decompose and enrich the soil with minerals,” Abbas says. “We are examining if applying biochar to seed coatings can deliver faster beneficial effects.”

Currently, Abbas and his collaborators are studying whether this seed treatment could protect soybeans—one of the most widely grown crops in the nation—from major threats like charcoal rot and frogeye leaf spot. The seed coating technology is generating significant interest within the agricultural industry.

“This research has had major impacts on agricultural biotechnology both nationally and internationally,” Abbas notes. “It is being evaluated by a major agricultural company for commercial development. What’s unique about this treatment is that its ingredients come from agriculture, not fossil fuels like petroleum, so it’s environmentally friendly.”

Bioplastic Coating Could Protect Both Birds and Seeds

Terrestrial birds, which live and forage primarily on the ground, can be more than just a nuisance for growers. These birds often feast on newly planted seeds, costing growers time, resources, and money. Simply put, the more seeds that are successfully planted and not consumed by birds, the higher the yields.